Audio and video streams are typically encoded into so called Elementary Streams (ES). The audio and video elementary streams are then packaged into Internet Protocol (IP) packets. Basically, different formats are supported by existing technology.
State-of-the-art bit stream-oriented quality assessment methods analyze the IP packets of the bit stream and derive an estimated quality measure such as a Mean Opinion Score (MOS) reflecting the audio-visual quality of the stream. To this aim, the elementary streams for audio and video are typically de-multiplexed. In further steps quality relevant parameters are extracted from the bit streams for audio and video. Finally, a mathematical model is used to calculate the quality measure from the extracted parameters for audio and video, or intermediate quality measures to be pooled to an overall visual quality estimate.
An IPTV system usually provides a head-end where the streams for all TV channels are aggregated and prepared. The prepared streams are distributed to the customer in a tree-like network structure. Regarding a single TV channel, all customers receive in principal the same stream. It is only the transmission that may cause specific changes to the stream, e.g. packet loss, that may have an influence on the quality.